Burns made his MLB debut in 2012, appearing in 17 games out of the San Diego bullpen. The 25-year-old posted a 5.50 ERA with 9.0 K/9 and 5.0 BB/9 in 18 innings at the MLB level. He spent most of the season at Triple-A, where he pitched to a 3.14 ERA with 10.6 K/9 and 2.3 BB/9 in 66 innings of relief.